Spyware is either cookies or executable code which "enhances" ones browsing experience. In my case, this included changing my toolbars, intercepting Google queries, and adding extra links to pages (e.g. "car" and "loan" linked to advertisers).
Some of this spyware was particularly vicious. Certain executables really messed up accessing the net -- even trying to find spyware antidotes. I finally picked up Spy Sweeper and that was able to fix most of the damage. Even so, registry keys from ipend have been difficult to get rid of.
Among the nasty stuff was adware from:
Then, Monday evening, I was hit with the Sasser virus. Windows unhelpfully kept informing me that the lsass.exe exited and that therefore a reboot was necessary. Luckily, after a few reboots I was able to get the antidote.
Useful tools: